Jensen



0. JENSEN.

ROCESS 0F PRODUCING PURE CONCENHATED NITRIC ACID AND TETROXID 0FNITROGEN. APPLICATION FILED Fa.4.1s19.

6002er' l nsaaaaa OLAF JENSEN, 0F GHRISTIANIA, NORWAY, ASSIG-NOR` ToNonsx HYnno-miiixrnisn KVAELSTOFAKTIESELSKAB, F CHRISTIANIA, NORWAY.

' rnocnss or rnciiucine PURE concnnraiirnn Nirfaic nein AND 'rnrnoxrn orv NITROGEN.

Specication of Letters Patent.

Application inea February i, i919. serial No. 27e-,eea

To all whom t may concern:

Beit known that l, OLAF JnNsnn, a su'bject of the King lof Norway, ofChristiania, Norway, have invented certain new and use-v fulImprovements in `lrocesses of Produc- 4ing Pure Concentrated Nitric Acidand 'lletroxid of Nitrogen; and I do hereby declare the following to bea full,.clear, and exact description of the invention, such as, willenable othersskilled in the arirto which it appertains to make and usethe same,'

. reference being vhad to the accompanying .acid accordingV to a knownmethod (dedrawings, and to letters or figures otreference markedthereon, which form a part of this specification. The invention relatesto the manufacture i of pure concentrated nitric acid from nitric acidcontaining nitrogen oxids and has for its object a process by means 'ofwhich pure nitrogen tetroxid can be obtained in a more efiicient mannerthan` according to the known methods.. 3

In the manufacture oi concentrated nitric scribed in the-German PatentNo. 225706) nitric acid of a concentration of only 80-90 per cent. isobtained if the pressure and temperature are not raised to a very highdegree, in which case it becomes y possible t0 v obtain an acid cfu-p to`95-9-6 per cent. The acid of a lower concentration obtainedby the useof moderate pressure and atordinary temperatures valso contains 20 to 30per" cent. nitrogen tetroxid. Attempts to produce from this impure AacidVapure highly concentrated' acid by distillation and de'- phlegmationvwill not meet w'ithsuccess.

rlhere will -be obtained only a'fred filming nitric acid, whiclit isvery dili'cultto purify Y and decolorize by heatingor by blowing acurrent of airthrough the saine.- The last named purification method ismoreover not y very economical in so far as it gives lhighly dilutednitrous gases, which again-mustl be further treated to produce liquidnitrogen tetroxid by freezingl or utilization by absorption in usualmanner.

According to the present invention highly v. concentrated pure nitricacid as well as pure N02-, which it is possible to use directly in theprocess, can be obtained.` The nitrogen tetroxid is first expelled in ablower column by means of vapors of concentrated nitric dephlegmationcolumn biler A.4 'llhevapor of in the condenser VK1 L I claim:

acid, the acid purified in' this manner being thereupon subjected to adephlegmation treatment, whereby it is separated into an acid of highconcentration (97-98 per cent.)

Patenten Decre, rete.

and an acid of low concentration, l((58-70 per cent.)

concentrated acid is with t The highly concentrated 'acid `escapes inthe form of vapor, while the less rawn in a liquid condition. A portionof the'acid vapors is condensed in the form of highly concen- -tratedacid, while .the rest is led to the blowing tower, in which theexpulsion of nitrogen oxids takes pllace. A plant for carrying thisprocess into effect in a continuous manner is illustrateddiagrammatically in introduced.- From the bottom 'of thisexpulsioncolumn the acid, which is now free from nitrogen oxids 'is ledto the top of the D2 and from the bottom of this to the highlyconcentrated nitric acid which vdistils oii from the to of the column D2is led to the condenser gi., where it is partially condensed. Thequantity of vapor, which is not condensed is ledinto the bottom-of thecolumn D1. The temperature' in this latter` -is controlled by means ofthe cooling eii'ect in the-condenser-KZ. From the top of.' D1- pure NO2escapes,

.below 21. C.. The pure ,highly concentrated z acid leaves the apparatusthrough the cooler 70 per cent. acid through the Qy K, and the coolerK4.

1.Ilrocess for the production' of concentrated nitric acid andnitrogentetroxid from. nitric acid containing ,nitrogen oxids comprisingthe steps of passing the acid in counter current tonitric acid vapors,

whereby nitrogen tetroxid'is expelled and I condensing thenitrogentetroxid subjecting the. acid purified by this treatment to, diswhichcan be condensedby cooling with water pure icc

tillation'and dephlegmatiomso as to obtain" i on the one hand diluteliquid acid and'on the other hand vapors of highly concentrated acid, a

portionof thel vapors of comen-- trated acid. being passed in,counter'current ice vapors of highly concentrated acid, and conintodilute liquid acid andl mai-,2te A densing a portion of the latter andreturnin the remainder for treatment of the acid to e purified. A g

In testimony fthat I claim the foregoing 15 as my invention, I havesigned my name in presence of two subscribing Witnesses OLAF JENSEN.

Witnesses:

C. VARMAN, ROLF GAARDER.

